Despite the undoubted counter-terrorism gains that have been made since September 11, 2001, it is clear that the threat from large Islamist terrorist groups has not been eradicated. Indeed, a number of Islamist terrorist organizations continue to aspire to conduct complex attacks against Western countries and interests around the world. The attacks carried out in Indonesia (2002), Madrid (2004), London (2005) and Mumbai (2008) are a stark reminder of the objectives of such groups.

The core al-Qaeda group still has the intent and capability of launching high impact attacks in the West while al-Qaeda in the Arabian Peninsula (AQAP) is among the most active and dangerous al-Qaeda affiliate, becoming a preeminent threat to Western interests. Al-Shabaab, Lashkar-e-Tayyiba (LeT) in Pakistan, al-Qaeda in the Islamic Maghreb (AQIM) and Boko Haram in Nigeria are also growing in influence and pose an increased risk within their regions of operation. In addition, there are fears jihadist groups currently operating in Syria are increasingly likely to carry out transnational attacks as the civil war in the country continues.

The relative strengths and weaknesses of each group are assessed below, along with their overall threat to the Western world.

Core al-Qaeda

The core al-Qaeda group remains fully committed to launching major terrorist attacks against the West. However, the probability of successfully carrying out a large-scale attack has been reduced as the group has been marginalized by strong counter-terrorism measures around the world such as the death of bin Laden and the elimination of other senior al-Qaeda operatives in sustained drone strikes. Although core al-Qaeda’s top leadership has demonstrated a prolonged commitment to acquire and use NBCR material, the risk of such an attack remains low.

Senior al-Qaeda leaders are therefore increasingly calling on individuals to carry out relatively unsophisticated attacks in their home countries while they attempt to plot more ambitious attacks. Notable intent and capabilities remain within al-Qaeda and the impact of any successful high-profile attack by the group in the West would likely be high.

Al-Qaeda In The Arabian Peninsula

AQAP was formed in January 2009 as the result of a merger between al-Qaeda’s Yemeni and Saudi branches. The group originally carried out attacks in Yemen and Saudi Arabia but has expanded operations to target the United States. AQAP was responsible for Umar Farouk Abdulmutallab’s attempted bombing of a Northwest Airlines flight as it approached Detroit on December 25, 2009 and the plot the following year that aimed to detonate two explosive-laden packages on cargo planes bound for the United States. Both plots ultimately failed but underscore the bomb-making skills and intent of the group.

The heightened risk from AQAP seemed to be confirmed in 2011 when National Counterterrorism Center (NCTC) Director Michael Leiter said the group could be the most significant risk to the United States. Since then, AQAP has been weakened by the deaths of its American-born leader, Anwar al-Awlaki, and other senior AQAP operatives in drone attacks. However, AQAP’s repeated attempts to assassinate high level Yemeni government officials and an attack on the country’s defense ministry in December 2013, which killed 52 people, have demonstrated its ability to regroup and continue to mount destructive attacks throughout the country.

Although the group’s capability outside of Yemen is lower, it continues to harbor ambitions to carry out complex and sophisticated attacks beyond its borders. Indeed, US intelligence services said they foiled a plot by AQAP to target a US bound passenger plane in May 2012 while another alleged large-scale plot by the group forced the mass closure of Western embassies across the Middle East and North Africa in August 2013.

Al-Shabaab

Al-Shabaab is the most prominent insurgent group in Somalia and is known to have successfully recruited American and European Muslims. It is reported to have enlisted 200 foreigners, with up to a quarter coming from the United Kingdom. The group declared it had merged with al-Qaeda in February 2012.

Despite being forced to retreat from Somalia’s capital of Mogadishu in 2011 and their southern stronghold of Kismayo in 2012 by Somali and African Union forces, al-Shabaab proved its transnational capability remains intact by launching the attack on the Westgate shopping mall in September 2013. It had also previously carried out a suicide attack in the Ugandan capital of Kampala on July 11, 2010, which killed more than 70 people.

However, al-Shabaab’s direct transnational intent has so far been limited to launching attacks against countries contributing troops to the African Union force in Somalia, which includes Kenya, Uganda, Ethiopia and Djibouti. In addition, the Westgate attack suggested that al-Shabaab’s capability outside of Somalia is limited to crude explosives such as grenades.